1. Field of the Invention
This invention relates to a color picture reproducing device with a color picture tube.
2. Description of the Prior Art
A color picture reproducing device having a three-electron gun in-line type color picture tube with first grids integrally formed and a color signal amplifier stage for supplying the primary color signals of red, blue and green to the corresponding cathodes of the color picture tube by transistor amplifier circuits, is used in a color television receiver, Model CT-938, manufactured by Hitachi Ltd. Company. In this known color picture reproducing apparatus, the correction of a variation in the cutoff voltages of the respective electron guns, or the adjustment of the white balance in the dark picture, mainly due to the assembling error of the electron guns, is performed by using variable resistors each connected between the emitter and ground of each transistor of which the collector and cathode are connected with each other. Further, the adjustment in the bright picture is performed by using a variable resistor provided between the emitter and the luminance signal supply terminal in order to adjust relatively the amplification degree of each transistor for the remaining transistors. The variation of the cutoff voltages is high, say, 100 V and the drive voltage for the transistor is the sum of a given amplitude voltage, the varied voltage and the first grid voltage. Therefore, in the conventional color picture reproducing apparatus, corresponding to the increment of the drive voltage by the varied voltage, the loss of the transistor or the collector load resistor increases. As the withstand voltage between the collector and emitter of the transistor increases, it is more difficult to manufacture transistors with good high-frequency characteristic. Therefore, transistors manufactured are expensive and uneconomical. Moreover, it makes it difficult to manufacture transistors operable in a wide band of frequency. This results in the picture reproduced with insufficient resolution.
In order to reduce the loss of the transistor, if the collector load resistance is made large, the cutoff frequency of the output circuit determined depending on the output capacity of the transistor, the cathode input capacity, the stray capacity among the wiring, and the collector load resistance, is reduced, leading to the picture reproduced with insufficient resolution.